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Oximeter cross-talk reduction

a technology of crosstalk and oximeter, applied in the field of oximeters, can solve problems such as phase offset problems

Active Publication Date: 2005-08-25
TYCO HEALTHCARE GRP LP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

One of the issues with each signal, for the red and infrared (IR), is cross-talk.
Such filtering can result in crosstalk when the filtering spreads out the red and IR pulses so they overlap.
This patent shows an approach where the same signal drives the red and IR at opposite phases, giving a phase offset problem.

Method used

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  • Oximeter cross-talk reduction

Examples

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Embodiment Construction

Overall System

[0016]FIG. 1 illustrates an embodiment of an oximetry system incorporating the present invention. A sensor 10 includes red and infrared LEDs and a photodetector. These are connected by a cable 12 to a board 14. LED drive current is provided by an LED drive interface 16. The received photocurrent from the sensor is provided to an I-V interface 18. The IR and red voltages are then provided to a sigma-delta interface 20 incorporating the present invention. The output of sigma-delta interface 20 is provided to a microcontroller 22. Microcontroller 22 includes flash memory for a program, and SRAM memory for data. The processor also includes a microprocessor chip 24 connected to a flash memory 26. Finally, a clock 28 is used and an interface 30 to a digital calibration in the sensor 10 is provided. A separate host 32 receives the processed information, as well as receiving an analog signal on a line 34 for providing an analog display.

Bandpass Filter

[0017]FIG. 2 is a blo...

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PUM

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Abstract

A method and apparatus for reducing cross-talk in an oximeter. The oximeter includes a band pass filter. The amount of cross-talk through the band pass filter is estimated. Based on this estimate, the corner frequencies of the band pass filter are adjusted when it is designed to minimize the cross-talk. In one embodiment, a calibration mode is performed when a sensor is attached to the oximeter. In the calibration mode, the signals are measured with first only the red LED on and then with only the IR LED on. Any signal measured in the off channel is assumed to be a result of cross-talk from the other channel. The magnitude of the cross-talk is determined as a percentage, and subsequently the percentage is multiplied by the actual signal and subtracted from the other LED signal as cross-talk compensation.

Description

BACKGROUND OF THE INVENTION [0001] The present invention relates to oximeters, and in particular to methods for reducing cross-talk between red and IR signals in pulse oximeters. [0002] Pulse oximetry is typically used to measure various blood chemistry characteristics including, but not limited to, the blood-oxygen saturation of hemoglobin in arterial blood, the volume of individual blood pulsations supplying the tissue, and the rate of blood pulsations corresponding to each heartbeat of a patient. Measurement of these characteristics has been accomplished by use of a non-invasive sensor which scatters light through a portion of the patient's tissue where blood perfuses the tissue, and photoelectrically senses the absorption of light at various wavelengths in such tissue. The amount of light absorbed is then used to calculate the amount of blood constituent being measured. [0003] The light scattered through the tissue is selected to be of one or more wavelengths that are absorbed b...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): A61B5/00
CPCA61B5/14551A61B5/725A61B5/7203
Inventor PETERSEN, ETHANCHEW, BRADFORD B.SHEA, WILLIAM
Owner TYCO HEALTHCARE GRP LP
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